Domain propagation arrangement

ABSTRACT

A SINGLE WALL DOMAIN CAN BE MADE TO DIVIDE INTO TWO BY STRETCHING THE DOMAIN AND BY SUPPLYING A CUTTING FIELD CONVENIENTLY BY MOVING ONE END OF THE DOMAIN ALONG A PATH BACK TOWARDS THE CENTER OF THE DOMAIN. INPUT ARRANGEMENTS ARE DESCRIBED IN WHICH THIS OPERATION IS CARRIED OUT IN RESPONSE TO A MAGNETIC FIELD ROTATING IN THE PLANE OF A SHEET IN WHICH SUCH DOMAINS ARE FORMED.

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United States Patent 3,555,527 DOMAIN PROPAGATION ARRANGEMENT Anthony J. Perneski, Martinsville, N.J., assignor to Bell Telephone Laboratories, Incorporated, Murray Hill and Berkeley Heights, NJ., a corporation of New York Filed Aug. 29, 1968, Ser. No. 756,210 Int. Cl. Gllc 11/14, 19/00 US. Cl. 340174 17 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION This invention relates to information processing apparatus and, more particularly, to such apparatus employing sheets of magnetic material in which single Wall domains can be moved.

BACKGROUND OF THE INVENTION A single wall domain is a magnetic domain encompassed by a single wall domain wall which closes upon itself and defines the boundary between the domain so encompassed and the surrounding regions of opposite polarity. The boundary of a single wall domain is independent of the boundary of the sheet in the plane in which it is moved and thus permits two-dimensional movement of the domain in the sheet. The Bell System Technical Journal, vol. XLVI, No. 8, October 1967, pages 1901 et seq., describes shift register operation employing single wall domains in sheets of rear earth orthoferrites.

A variety of propagation techniques for moving single wall domains have been developed. A typical magnetic sheet in which single wall domains can be moved is characterized by a preferred direction for magnetization out of the plane of the sheet. Let us adopt the convention that the magnetization of a single wall domain is in a positive direction along an axis assumed normal to the sheet while the magnetization of the remainder of the sheet is in a negative direction along that axis. In this context, a single wall domain may be represented as an encircled plus sign where the circle represents the single domain wall. A discrete conductor in the form of a circular loop on the surface of the sheet generates a field which is positive or negative along that, axis dependent on the polarity of current in the loop. Such a loop in a position offset from a domain generates an attracting (positive) field when pulsed, The domain sees that field (actually field gradient) and moves to a least energy position in response. By pulsing consecutively offset loops, the domain can be moved to any arbitrary position in the sheet.

These propagation loops permit logic operation to be effected between neighboring domains by turning to account interaction etiects between selected ones of those domains. But the loop geometry of the conductors occupies a greater minimum space than would be required if the constraint of discrete propagation conductors could be obviated.

Copending patent application Ser. No. 732,705, filed May 28, 1968 for A. H. Bobeck, among others, describes implementations for achieving propagation of single wall domains without discrete propagation conductors. An overlay of a soft magnetic material such as permalloy defines a propagation channel for domains in a suitable magnetic sheet. The overlay is patterned in the form of consecutive bars and T shapes which support a moving and repetitive magnetic pole configuration which is attracting to the domains. A magnetic field rotating in the plane of the sheet (transverse) causes the pole pattern to change in a manner to attract domains from input to output positions. Although such an arrangement is simpler to fabricate than an arrangement requiring discrete propagation conductors and permits increased packing densities, it is not capable of performing all the logic functions achievable with the discrete conductors.

A variety of compromises have been worked out to gain the advantages of both approaches. For example, a single conductor for each propagation channel along with a permalloy overlay of prescribed geometry permits certain logic operations but still does not require discrete propagation conductors.

Regardless of the mode of propagation and the associated logic capabilities, it is important that domains be introduced controllably into the magnetic sheet for propagation. But a typical sheet of magnetic material suitable for the propagation of single wall domains and saturated magnetically in a negative direction requires thousands of oersteds to nucleate a single wall domain. Movement of a domain, on the other hand, requires only a few oersteds.

To avoid excessive power demands, techniques have been devised to sever a domain from a source of domains at power levels comparable to those required for domain propagation; that is about the few oersted level. Copending application Ser. No. 579,931, filed Sept. 16, 1966 for A. H. Bobeck, U. P, Gianola, R. C. Sherwood, and W. Shockley (now Pat. 3,460,116) describes one such input arrangement where an area of positive magnetization is defined by a current in a conductor outlining the area. A hairpin-shaped input conductor, overlying the area, may be used to generate a field for severing a portion of the area in response to an input pulse of appropriate polarity.

An object of this invention is to provide an input arrangement for generating single wall domains at relatively low fields and in the absence of input conductors or area outlining conductors.

BRIEF DESCRIPTION OF THE INVENTION It has been discovered that a single wall domain can be stretched and then separated into two, in response to a rotating transverse field, by the controlled movement of an additional domain, by an end of that domain, or by a field provided by an appropriately placed permalloy overlay. This discovery is turned to account in one embodiment where a propagation channel for single wall domains is defined in a magnetic sheet by bar and T-shaped overlays of permalloy. A permalloy disk having a single wall domain permanently associated therewith exhibits pole patterns moving in a first direction thereabout in response to a field rotating in the plane of the sheet. The bar and T pattern is of a geometry to exhibit poles moving in a second direction away from the disk also in response to such a rotating field. A domain following the attracting poles around the periphery of the disk is stretched out along both the bar and T arrangement and the disk periphery until the end of the domain stretching around the disk makes almost a full cycle. At this juncture, the domain divides into two, one following the bar and T, the other moving about the disk again being stretched out as before.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic representation of a single wall domain propagating arrangement including an input in accordance with this invention;

FIGS. 2, 3, 4, 5, 6, 7, and 8 are fragmentary schematic representations of the input portion of the arrangement of FIG. 1 showing the magnetic conditions thereof in response to a rotating transverse field during operation and the orientations of the field for efifecting these conditions;

FIG. 9 is a schematic representation of a multichannel domain propagation arrangement including a plurality of input configurations in accordance with this invention; and

FIGS. -15 are fragmentary schematic representations of alternative input arrangements in accordance with this invention.

DETAILED DESCRIPTION FIG. 1 shows a domain propagation arrangement 10 including a sheet 11 in which single wall domains can be propagated.

A plurality of channels for domain propagation are defined by bar and T-shaped overlays 13 and 14 aligned between input and output positions, each channel starting at the left as viewed in FIG. 1 with a disk-shaped overlay 15. Domains are moved by following the attracting pole concentrations generated in the overlays in response to a rotating transverse magnetic field. The source of the rotating field is represented by block 16 so designated and may comprise two orthogonal sets of coils positioned along broken lines B and B to which properly phased sine waves or pulses are applied under the control of control circuit 17.

The input to the propagation channel is defined to the left as viewed in FIG. 1 and includes the permalloy disk 15. A domain D is provided in a manner such that it is permanently associated with disk 15, moving about the periphery thereof in response to the rotating transverse field. A demagnetized sheet, to which a field of a polarity to contract domains is applied, exhibits a number of domains for this purpose.

FIGS. 2 through 8 show the magnetic conditions of the input as the transverse field rotates through a single cycle. FIG. 2 shows the condition when a transverse field H is in an arbitrary initial orientation to the left as represented by the arrow so designated in FIG. 2. Positive poles accumulate to the left of disk negative poles to the right. For a disk on the top of sheet 11, positive poles attract a domain in accordance with the assumed convention. When the disk is on the bottom of sheet 11, negative poles attract a domain. The same is true of the bar and T geometry which may or may not be on the same side of sheet 11 as the disk. A domain D is seen to underlie the positive poles.

In FIG. 3, the transverse field is shown directed downward. The resulting pole concentration is as represented by the plus and minus signs. The domain moves to the bottom of disk 15 as viewed.

FIG. 4 shows the field directed to the right. The strongest positive pole is now at the right extreme of the extension 16 of disk 15. Yet other positive poles are on the right edge of the disk. The domain assumes the position and shape shown.

In FIG. 5, the transverse field is directed upward. When the field is in this orientation, each of the nearest bar 13 and the disk has a strong pole distribution attracting domain D. The domain stretches as a result. This stretching continues as the field rotates still further counterclockwise as shown in FIGS. 6 and 7. The specific contour of the domain in each figure is due to the repelling effect of negative poles on disk 15. FIG. 7 depicts the domain configuration just as the domain is about to divide into two.

FIG. 8 shows the initial domain at an advanced position on a T-shaped overlay 12 whereas a domain D' is in the position shown for domain D in FIG. 4. Of course, the designations of the domains are arbitrary; the mechanism for domain division is not fully understood. It is clearly observed, however, that a domain does stay associated with disk 15 and a domain is generated therefrom in response to a rotating transverse field.

That same transverse field also provides the moving pole patterns which attract domains along the propagation channel. But propagation along the channel requires typically a 10 oersted field or more, whereas a domain input as shown in FIGS. 2-8 requires typically more than 20 oersteds.

The difference in the amplitude requirements of the transverse field for input and propagation provides the mechanism for selective introduction of domains. Therefore, domain propagation continues at about a 10 oersted field unless a domain representing say a binary one is desired. The amplitude of the rotating field is increased to 20 oersteds for the next cycle for introducing the desired domain. Thereafter, the amplitude may he reduced to conserve power.

The transverse field may be suitably altered, of course, by a change in the phase relationship of the sine waves generated by source 16 of FIG. 1 or by an overlap of pulses if pulse techniques are employed.

The amplitude of the rotating field need not be high during the entire cycle during which the introduction of a domain is desired. A domain can be stretched to about the point shown in FIG. 6 at a relatively low transverse field amplitude. At the point shown in FIG. 6, the higher amplitude is required. Accordingly, the higher amplitude is necessary, ideally, for about one-quarter cycle. Source 16 of FIG. 1 is considered to include apparatus capable of operating in this manner under the control of a control circuit 17 to which it is connected.

We have now discussed the selective introduction of a single wall domain for synchronous movement along a propagation channel. It is clear also that the presence and absence of a domain at a particular position indicates a binary one and a binary zero respectively. An information representative pattern of domains is moved to an output position in a manner clear from FIG. 8 following the attracting pole patterns along the propagation channel.

An output position is shown in FIG. 1 defined by a. conductor loop 19 encompassing a terminal position in the channel. Conductor 19 is connected between an interrogate pulse source 20 and ground. A conductor loop 21 also encompasses the same terminal position, connected between a utilization circuit 22 and ground. Each time a rotation of the transverse field produces the magnetic condition of FIG. 8, source 20 pulses conductor 19 to generate a field to collapse domains in the terminal position. If a domain is occupying the terminal position when the collapse field is applied, a pulse is generated in conductor 21 for detection by circuit 22. Source 20 and circuit 22 are connected to control circuit 17 for synchronization and energization.

The various sources and circuits herein may be any such circuits capable of operating in accordance with this invention.

The selective introduction of a single wall domain into a propagation (shift register) channel in the absence of peripheral conductors to the input has now been described. The introduction of a domain into a selected one of many channels also can be achieved in accordance with this invention.

The geometry of an overlay determines the amplitude of the rotating transverse field which generates domains as described. Input overlay geometries can be designed to enable the amplitude of the transverse field to determine the channel into which a domain is introduced.

FIG. 9 shows a sheet in which a plurality of propagation channels a, b n are defined by an alternative bar and T overlay arrangement. Each of these channels has an input overlay, of different geometry, on the opposite side of sheet 110 from the bar and T overlays. Each works essentially as described in connection with FIGS. 2 through 8, but the exact configuration of the stretching domain, in each instance, may differ.

The input overlay to channel a is rectangular in form and about one-eight mil thick. A domain moving about the periphery of the overlay in response to a rotating transverse field divides as described when the amplitude of the transverse field is increased to a minimum of about 20 oersteds. The input overlay to channel b, on the other hand, is a disk 13,000 angstrom units (approximately one-twentieth mil) thick. This overlay operates to generate domains as described when the transverse field is increased to 50 oersteds. The overlay of channel it is a cross in form, 5,800 angstrom units thick and operates at about 40 oersteds. It is clear then that the introduction of a domain in channels a, b, and n selectively depends on an appropriately timed change of from about 7 oersteds to 20, 40, and 50 oersteds in the amplitude of the transverse field for selective introduction of domains, respectively.

Actually, domain division in a selected channel takes place over a range of fields. By a judicious choice of input overlay geometry, different combinations of channels can be selected for domain division by the provision of a field in an appropriate range for each of the channels selected.

As was described hereinbefore, single wall domains are capable of movement in two dimensions. Therefore the horizontal channels of FIG. 9 can be oriented vertically with like results. Moreover, horizontal and vertical channels can be realized with a generalized pattern of overlays which permits domain movement in X and Y directions. Domains can be introduced at desired points in such an arrangement for movement to selected channels.

It is possible further, in accordance with this invention to introduce domains into more than one channel from a given input overlay. This possibility stems from the fact that the amplitude of the transverse field need be increased during only one-quarter cycle ideally. During different quarter cycles, that amplitude can be increased, as described, for genemting domains in correspondingly oriented channels.

FIGS. 10-13 show an illustrative arrangement where domains are introduced selectively into a plurality of channels C1, C2 The magnetic domain (D) configuration for each channel is similar to that shown in FIGS. 28. A domain is generated, or not, in each channel depending upon the amplitude of the rotating field as the field is oriented ideally through the last quarter cycle before being oriented in the direction of the selected channel.

The shape of an input overlay along with controlled changes in the amplitude of a rotating transverse field provides a combination of implementations which provide considerable flexibility in the provision of domains for movement in selected propagation channels in the absence of peripheral conductors.

The invention has been described in terms of a domain turned on itself to cause division. It should be clear that that domain, when so turned, operates to provide a field at the point of division. That field can be provided in other ways of course. For example, FIG. 7 shows a broken rectangle representing a permalloy bar on the opposite side of sheet 11 from the bar and T arrangement there. Bar 1'5 includes plus poles at its bottom as viewed. But since that bar is on the opposite side of sheet 11, positive poles repel domains and a field is generated thereby to help collapse domains.

An arrangement of three parallel bars as shown in FIG. 14 also is useful to generate domains in much the same manner inasmuch as the arrangement generates the appropriately oriented pole configurations and thus fields in response to a transverse field. In FIG. 14, bars 15" are of relatively low coercive force material whereas bar 15' is of high coercive force material. A domain D positioned as shown in FIG. 15 grows to the position shown in FIG. 14 in response to a field H1 of an amplitude insufficient to switch bar 15' but sufiicient to establish the pole configuration shown. In FIG. 15 the amplitude of that field is increased to H2 above that necessary to switch bar 15'. Consequently, the domain divides into two, D and D1 as shown, in response to the new pole configuration. Such fields are generated in a manner consistent with the requirements of a rotating transverse field which operates to shuttle domain D up and down on bar 15'', as viewed, between consecutive divisions while domain D 1 follows an associated bar and T arrangement to an output position.

What has been described is considered only illustrative of the principles of this invention. Therefore, various other embodiments can be devised by one skilled in the art in accordance with these principles without departing from the spirit and scope of this invention.

What is claimed is:

1. In combination, a sheet of material in which a single wall domain can be moved, a channel-defining first overlay adjacent said sheet and having a geometry for generating magnetic pole concentrations moving in a first direction from a reference position in said channel in response to a field rotating in the plane of said sheet for attracting domains from an input to an output position in said channel, and a :first input overlay adjacent said sheet at said input position and of a geometry to generate pole concentrations moving from said reference position in a second direction opposite to said first direction in response to said rotating field, and means for detecting the presence and absence of said domains at said output position.

2. A combination in. accordance with claim 1 including a single wall domain magnetically coupled to said input overlay in a position to be expanded by said magnetic pole concentrations moving in said first and second directions, and means for generating said rotating field.

3. A combination in accordance with claim. 2 also including means for generating a field to collapse domains at said reference position.

4. A combination in accordance with claim 3 wherein said means for generating a field to collapse domains coma prises a single wall domain and means for moving said last-mentioned domain into said reference position.

5. A combination in accordance with claim 3 wherein said input overlay is of closed loop geometry to generate pole concentrations which move in a closed loop back to said reference position for generating said field to collapse domains there.

6. A combination in accordance with claim 5 wherein said input overlay comprises a soft magnetic disk for generating pole concentrations moving about the periphery thereof in response to a rotating transverse field.

7. A combination in accordance with claim 6 also including means for modifying said .rotating transverse field for selectively generating pole concentrations sufficient to expand said single wall domain associated with said disk.

8. A combination in accordance with claim 7 wherein said last-mentioned means comprises means for controllably increasing the amplitude of said rotating transverse field.

9. A combination in accordance with claim 5 including a second input overlay of a geometry difierent from said first input overlay and an associated second channeldefining overlay for generating magnetic pole concentrations moving in a first and a second direction from a reference position in that channel, said combination also including means for modifying said rotating transverse field in -a manner to increase said pole concentrations to expand a domain associated with said first and second input overlays selectively.

10. A combination in accordance with claim 9 wherein said means for modifying said rotating transverse field comprises means for changing the amplitude of said rotating transverse field in a manner and for a time to enable said moving pole concentrations to expand a domain selectively at said first and second input overlays.

11. A combination in accordance with claim 3 wherein said means for generating a field to collapse domains comprises a magnetic overlay in a position and of a coercive force to provide a repelling pole concentration at said reference position in response to said transverse field.

12. A combination in accordance with claim 5 including first and second channel-defining overlays oriented radially with respect to said closed loop and means for selectively generating in said overlays pole concentrations moving away from said closed loop and of a strength to expand said domain.

13. In combination, a sheet of magnetic material in which single wall domains can be moved, means for generating first and second magnetic pole concentrations moving in first and second directions from a reference position in response to a magnetic field rotating in the plane of said sheet, and means for providing at said reference position a single wall domain for expansion in response to the movement of said pole concentrations.

14. A combination in accordance with claim 13 also including means for selectively changing the strength of said pole concentrations.

15. In combination, a sheet of magnetic material in which single wall domains can be moved, and means for generating first and second magnetic pole concentrations moving incrementally in first and second directions from a first position in said sheet in a manner to stretch a single wall domain therebetween.

16.. A combination in accordance with claim 15 also including means for providing a single wall domain at said first position.

17. A combination in accordance with claim 16 also including means for generating a field of a polarity to collapse a domain at said first position.

References Cited UNITED STATES PATENTS STANLEY M. URYNOWICZ, 111., Primary Examiner 

